1. Field Of The Invention
This invention relates to the fluid ends of high pressure reciprocating pumps, and more particularly, to a pump fluid end having a built-in accumulator and which uses frictional clamping to connect the pump plunger to a push rod in the drive end of the pump.
2. Description Of The Prior Art
Hydraulic jetting, wherein fluids such as water are pumped at high pressure through jetting nozzles, is used for a variety of applications such as industrial cleaning. One industrial cleaning application in which hydraulic jetting is particularly well adapted is the cleaning of the interiors and exteriors of tubes in heat exchangers and boilers. Water jetting is also used for drilling and cutting of materials.
In hydraulic jetting, the fluids are usually pumped at ultra high pressure, for example 35,000 psi, and specialized pumping equipment is required. Typically, reciprocating plunger pumps are used. In such pumps, the drive end typically includes a crosshead to which the pump plunger is connected. Even with multiple plunger pumps, there is a problem with discharge pressure fluctuation due to the low capacity of typical water jetting systems. In an effort to minimize flow problems with such pressure fluctuations, volume chambers or accumulators are connected between the pump and the jetting system. These external accumulators solve the problem of pressure fluctuations, but do not eliminate another problem with fatigue failure of cyclically pressured components in the pump. Such fatigue problems generally occur at locations of relatively high stress concentrations, such as cyclically loaded threads. The pump of the present invention solves both the pressure fluctuation and the fatigue failure problems by providing internal volume chambers or accumulators which internally dampen fluid pressure fluctuations in the fluid end of the pump, thereby minimizing fatigue loading on pump components.
To obtain maximum plunger life in ultra high pressure pumps, the plungers are preferably made of very hard material such as carbide or ceramic. An unfortunate side effect is that such materials are brittle and more subject to failure due to impact loading. Such a problem is compounded by stress concentrations induced in attaching the plunger to the drive end of the pump such as by threaded engagement. The present invention solves this problem by providing a friction collet which clamps around the pump plunger and substantially evenly distributes the loading thereon, thus reducing induced stress concentrations and the accompanying problems.